It is becoming more common for enterprises to employ a wide area network (WAN) to connect several smaller or branch offices to the main office. This is true for both data networks and voice networks. The smaller offices may rely upon the WAN connection to the main office for many types of services, including call management, routing and directory services. Typically, the call management, routing and directory service may be controlled by a central entity, referred to here as a call manager.
There may be several call managers coordinating different regions of the WAN, based upon enterprise function, geography, size, etc. In addition, the call manager functions may be distributed across several different network devices. No limitation upon implementation or configuration of a call management function is implied or intended by the use of the term ‘call manager.’
Issues may arise at the branch offices if the WAN becomes inoperative or loses communication. With the loss of the call manager, the branch office may not be able to make phone calls, in addition to losing their connections to the data networks. This is unacceptable for stable operations.
A solution to these issues may be referred to as ‘fallback’ operations. In fallback operations, a fallback device or devices have been designated to assume the functions of call manager during WAN failure. Secondary devices may contact the fallback device during fallback operations, and the fallback device will need to verify its identity. The secondary device may be a secondary call manager that is assuming operations from the primary call manager, or a network phone desiring fallback services. The phones or data network devices that will rely upon this fallback device are configured with this information by the call manager during normal WAN operation.
However, fallback operations have not previously encompassed secure operations, in which secure phones are listed in a list of trusted devices, on a scale broad enough to provide secure operations for larger operations.